Henry Ernest Dudeney/Modern Puzzles/32 - Riding in the Wind

Modern Puzzles by Henry Ernest Dudeney: $32$

Riding in the Wind

A man on a bicycle rode a mile in $3$ minutes with the wind at his back,

but it took him $4$ minutes to return against the wind.

How long would it take him to ride a mile if there was no wind?

Some will say that the average of $3$ and $4$ is $3 \tfrac 1 2$, and it would take him $3 \tfrac 1 2$ minutes.

That answer is entirely wrong.

Sources

• 1926: Henry Ernest Dudeney: Modern Puzzles ... (previous) ... (next): Arithmetical and Algebraical Problems: Locomotion and Speed Puzzles: $32$. -- Riding in the Wind
• 1968: Henry Ernest Dudeney: 536 Puzzles & Curious Problems ... (previous) ... (next): Arithmetical and Algebraical Problems: Speed & Distance Puzzles: $60$. Riding in the Wind